Mean spacing between Hemoglobin molecules

[Krazer101]

Homework Statement

Calculate the mean spacing between hemoglobin molecules inside a red blood cell?

Homework Equations

Diameter of red blood cell = 5 microns
3*10^8 hemoglobin molecules in each red blood cell
Volume of hemoglobin molecule = 8.71*10^-26 m

The Attempt at a Solution

I assume we take the blood cell to be a spherical model, therefore we can find the volume of the cell. I am having trouble understanding how to use this data to find spacing inside a sphere.

 

[Krazer101]

anyone know where to start? I was thinking to use the density of the red blood cell but I am still having trouble figuring out how to eventually get to mean spacing

 

[Borek]

I would treat it as a simple geometry. Calculate volume available to each hemoglobin molecules, assume it sits in the center of a cube, calculate cube edge length.

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[Krazer101]

So if we take the molecule in the center, then would the separation be the distance between the center of two cubes? The separation is the cube length? I am having trouble understanding how you determine cube length. Are we supposing the molecule takes up all the possible room in the cube?

 

[Borek]

So if we take the molecule in the center, then would the separation be the distance between the center of two cubes? The separation is the cube length?

It is the same.

I am having trouble understanding how you determine cube length.

Oh come on, what is the formula for cube volume?

Are we supposing the molecule takes up all the possible room in the cube?

Doesn't matter, even if it doesn't take whole volume. Space can be filled with anything - water for example.

There is a possible problem if given molecule volume is higher than the cube volume, that would mean something is wrong.

 

[Krazer101]

Thank you, my main problem was understanding what would happen if the molecule did not completely occupy the cube or so. Thanks for explaining it to me.